单项选择题A.On short trips.B.On long trips.C.When flying over cities.D.When flying at high altitude.
单项选择题A.They defend the bone against viruses.B.They break down bone tissue.C.They prevent oxygen from entering the bone. D) They connect the bone to muscle tissue.
单项选择题A.People’s health.B.People’s lives and futures.C.The end of the world.D.The Great Depression of 1929.
单项选择题A.She was asked to call the chairman’s wife.B.She was asked to make a copy of English final exam.C.She was asked to go to the chairman’s wife’s office.D.She 4vas asked to retake the final exam.
单项选择题A.Two different types of bones in the human body.B.How bones help the body move.C.How bones continuously repair themselves.D.The chemical composition of human bones.